SYNOPSIS

DESCRIPTION

Note: this system call is (since Linux 3.16) deprecated and will
eventually be replaced by a slower in-kernel emulation. Those few
applications that use this system call should consider migrating to
alternatives.
The remap_file_pages() system call is used to create a nonlinear
mapping, that is, a mapping in which the pages of the file are mapped
into a nonsequential order in memory. The advantage of using
remap_file_pages() over using repeated calls to mmap(2) is that the
former approach does not require the kernel to create additional VMA
(Virtual Memory Area) data structures.
To create a nonlinear mapping we perform the following steps:
1. Use mmap(2) to create a mapping (which is initially linear). This
mapping must be created with the MAP_SHARED flag.
2. Use one or more calls to remap_file_pages() to rearrange the
correspondence between the pages of the mapping and the pages of the
file. It is possible to map the same page of a file into multiple
locations within the mapped region.
The pgoff and size arguments specify the region of the file that is to
be relocated within the mapping: pgoff is a file offset in units of the
system page size; size is the length of the region in bytes.
The addr argument serves two purposes. First, it identifies the
mapping whose pages we want to rearrange. Thus, addr must be an
address that falls within a region previously mapped by a call to
mmap(2). Second, addr specifies the address at which the file pages
identified by pgoff and size will be placed.
The values specified in addr and size should be multiples of the system
page size. If they are not, then the kernel rounds both values down to
the nearest multiple of the page size.
The prot argument must be specified as 0.
The flags argument has the same meaning as for mmap(2), but all flags
other than MAP_NONBLOCK are ignored.

RETURNVALUE

On success, remap_file_pages() returns 0. On error, -1 is returned,
and errno is set appropriately.

ERRORS

EINVALaddr does not refer to a valid mapping created with the
MAP_SHARED flag.
EINVALaddr, size, prot, or pgoff is invalid.

VERSIONS

The remap_file_pages() system call appeared in Linux 2.5.46; glibc
support was added in version 2.3.3.

CONFORMINGTO

The remap_file_pages() system call is Linux-specific.

NOTES

Since Linux 2.6.23, remap_file_pages() creates non-linear mappings only
on in-memory file systems such as tmpfs, hugetlbfs or ramfs. On
filesystems with a backing store, remap_file_pages() is not much more
efficient than using mmap(2) to adjust which parts of the file are
mapped to which addresses.

SEEALSO

COLOPHON

This page is part of release 4.04 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
http://www.kernel.org/doc/man-pages/.